“What [the Port Authority is] going to do with that information is say, OK, are there any adjustments that need to be made in terms of critical equipment. The World Trade Center site is commercial space. So the standard is going to be flood-proofing it. There’s a bunch of different ways you can do that.”

Between 150 and 200 million gallons of the Hudson River water gushed into the trade-center site during Hurricane Sandy.

But officials said the site would be able to withstand flooding once the immense space fills in.

“It’s a hole in the ground,” explained one official. “Just by completing the site alone would minimize the damage.” “It’s enormously complex,” said Jordan Barowitz, a Durst executive.

“We are confident there will be no flooding risk in these towers even under the 100-year scenario,” said Silverstein spokesman Dara McQuillian. “Nevertheless, all critical building systems will be located out of harm’s way for any hypothetical flooding scenario.”

An official at the 9/11 memorial and museum said plans were drawn up even before the storm to preserve artifacts, and further steps are now being taken to mitigate flooding.

FEMA had earlier reported that the number of buildings citywide within flood zones had doubled from 35,000 to 70,000.

That’s going to force many owners to either lift their homes above the FEMA flood level for their neighborhood, or face higher-flood insurance bills starting as early as 2015.

The elevation option isn’t available to skyscrapers. Mike Klitzke of FEMA said owners of high rises might have to “give up their basement floor” or relocate mechanical equipment to higher floors to keep insurance rates in check.

“Some buildings in some areas actually have dykes around them,” he noted.

Elected officials and downtown landlords declined comment, saying they were still examining the FEMA maps.

The Durst Organization, which owns 90 apartments in three- and four-story buildings along Front Street near the South Street Seaport, has already begun shifting their heating and cooling units from basements to rooftops.